Pneumatic cannon not firing consistently – help needed

[Driftboss3d]

Hi everyone,
I’ve been building a pneumatic cannon using 2" PVC, a 120 psi compressor, and a quick-connect valve, but I’m having an issue: the spud is only firing reliably about 1 in 3 shots. The pressure gauge reads full, the valve seems to open correctly, and everything is sealed, but the projectile either dribbles out slowly or doesn’t launch at all.
Has anyone else seen this kind of intermittent performance? What checks or tweaks would you recommend (valve timing, barrel length, seal quality) to get consistent launches?